You can't trust most people with a gun. That's the problem. Guns also bring tension to most situations. How often do you visit people with a pistol attached to your hip? Do they all go, "Oh, yeah, feel even safer now that you're here." Probably not - they're worried you're going to do something stupid and shoot them.
No one I know feels safer with armed police around and tensions frequently escalate with them around. We all go, "this man has a gun and could kill us - he will do it too because he knows he will get away clean and free."
Training isn't sufficient. If there are real consequences for police and it shows that they face the same consequences the rest of us do for many years - maybe then. But that day will not be for 10+ years. For now, it's much easier to say and act on taking away their weapons that are meant to kill people.